2,2-Bis(fluoroalkyl)oxiranes such as 2,2-bis(trifluoromethyl)oxirane are partially fluorinated oxirane compounds. Since these oxiranes are susceptible to ring opening using various nucleophilic reagents, they are regarded promising in the field of photolithography or the like as a building block for fluoroalcohol skeleton as indicated in Patent Documents 1 and 2.
In the industry, these oxiranes are prepared by oxidation of fluorinated olefins. The direct oxidation method of reacting fluorinated olefins with oxygen is known from Patent Documents 1 and 3. Reaction with a metal hypochlorite as an oxidizing agent in the presence of a phase transfer catalyst is reported in Patent Document 2 and Non-Patent Document 1. In either method, the starting reactant or fluorinated olefin, which is gaseous, is difficult to handle and leaves concern about harm by vapor inhalation. In the direct oxidation method, toxic by-products such as hexafluoroacetone form. With respect to handling of the starting fluorinated olefins and the by-products which are gas or low-boiling liquid, a plant for large volume synthesis may be modified so as to ensure safe reaction. In the case of middle to small scale systems, typically multi-purpose reactors, however, the safety measure is uncertain and problems are left.
The foregoing oxiranes find a typical application as photoacid generators in the photolithography. Patent Document 4 describes that triphenylsulfonium 2-acyloxy-3,3,3-trifluoromethyl-2-trifluoromethylpropanesulfonate is prepared by starting with 2,2-bis(trifluoromethyl)oxirane and effecting ring-opening reaction with a hydrogensulfite. For a safe and consistent supply of the oxiranes which are useful reactants for such photoresist components, a method capable of readily preparing the oxiranes is desired.